For patients who have to permanently monitor the concentration of a specific analyte in the body and provide to the body medicaments for adapting this analyte concentration to physiological values, a considerable effort arises. So, for example patients with diabetes have to measure multiple times a day the blood glucose values which are used as a basis for a therapy decision. In doing so, the skin is perforated for example with a lancet and the thereby emerging blood is applied on a measuring strip as part of a measuring system. After availability of the measurement value the insulin dose is calculated wherein the insulin is injected into the subcutaneous tissue by means of a needle. This measurement/injection cycle is associated with two skin penetrations causing pain. Further, the insulin is administered in a “non-physiological” dosage. For optimizing the uniform dosage, insulin pumps have been developed which continuously deliver the insulin through an implantable catheter. Besides the advantage of the continuous delivery of the insulin, the pump catheter may reside in the tissue for a longer time, whereby a multiple piercing is omitted and the inconveniences associated therewith can be avoided.
WO 2010/142590 discloses a device for the transcutaneous, in vivo measurement of the concentration of at least one analyte in a living organism, comprising a carrier which can be introduced into the organism, and a luminescence indicator, which is immobilized on the carrier and which reacts to a change in the concentration of the analyte to be measured with a change in at least one optical property, wherein the luminescence indicator is transcutaneously connected to a source for providing the excitation radiation and a detector for detecting the measuring radiation. The luminescence indicator is immobilized on the outer circumference of a catheter, which is used to dispense a fluid medium, for example a medication, into the organism or to drain a body fluid.
Hence, the system according to WO 2010/142590 provides a compact device for measuring the glucose level. However, in the unlikely event of a failure of the luminescence indicator, a measurement of the glucose level is no longer reliably possible.
US 2013/0060105 discloses a continuous glucose monitoring system which may include a hand-held monitor, a transmitter, an insulin pump, and an orthogonally redundant glucose sensor, which may comprise an optical glucose sensor and a non-optical glucose sensor. The former may be a fiber optical sensor, including a competitive glucose binding affinity assay with a glucose analog and a luminophore-labeled glucose receptor, which is interrogated by an optical interrogating system, for instance a stacked planar integrated optical system. The non-optical sensor may be an electrochemical sensor having a plurality of electrodes distributed along the length thereof. Proximal portions of the optical and electrochemical sensors may be housed inside the transmitter and operationally coupled with instrumentation for, for instance, receiving signals from the sensors, converting to respective glucose values, and communicating the glucose values. The sensors' proximal portions may be inserted into a user's body via a single delivery needle and may be co-located inside the user's body.
The system according to US 2013/0060105 has the advantage that the glucose level measurement is still possible when one of the two orthogonal redundant glucose sensor fails. It is however a shortcoming of such a system that the resulting devices require a lot of space.